Sized paper and method of making same



SIZED PAPER AND METHOD OF MAKING SAME Cyrus A. Weisgerber, Chadds Ford, Pa., assignor to Hercules Powder Company, Wilmington, Del., a corpora- This invention relates to improvements in the internal sizing of paper with aqueous ketene dimer emulsions.

It is known that ketene dimers are effective sizing agents for paper. These materials, as such, are insoluble in water and, in order to facilitate their use in the paper industry, they have been mixed with emulsifying agents which make them readily dispersible in water for the formation of aqueous emulsions. These emulsions, however, are usually nonionic and when used for the internal sizing of paper, the retention of the ketene dimer by the cellulose fibers is not complete, with the result that some of the material goes towaste with the discarded white water.

A principal object of the present invention is the provision of a process for the internal sizing of paper with aqueous emulsions of ketene dimers wherein improved retention of the ketene dimer by the paper fibers is ob tained with resultant economies in operation.

In accordance with the invention, it has been found that in the internal sizing of paper with ketene dimers wherein an aqueous emulsion of a ketene dimer is added to a dilute aqueous pulp suspension and the pulp then sheeted and dried, improved retention of the dimer by the paper fibers may be obtained by incorporating in the aqueous pulp suspension from about 0.001% to about 0.2% by weight, based on the weight of pulp, of a polymer of an alkyleneimine containing not more than four'carbon' atoms. By virtue of this increased retention, it is possible to obtain a greater degree of sizing with the same amount of ketene dimer added or an water.

In a preferred procedure for carrying out the invention, the aqueous emulsion of ketene dimer containing the'poly(alkyleneimine) admixed therewith, is added to an aqueous suspension of cellulosic papermaking fibers, as in the beater of a papermaking system and the pulp then formed into sheets or webs in the conventional manner. Optimum results are obtained if, during sheet formation, the aqueous suspension is maintained at a pH within the range from about 4.5 to about 8 and preferably within the range from about 4.5 to about 5.5. The poly(alkyleneimine) is preferably added to the aqueous emulsion of ketene dimer in the form of an aqueous solution or dispersion and just prior to the introduction of same into the aqueous suspension of papermaking fibers. The addition should, of course, be accompanied with suflicient agitation or stirring to insure thorough admixture of the poly(alkyleneimine) solution with the aqueous emulsion.

. While it is preferred, as indicated, to add the aqueous emulsion of ketene dimer and poly(alkyleneimine) to the aqueous suspension of pulp in admixture with each other, it is also possible to add the two separately- Thus,

the poly(alkyleneimine), preferably in the form of an- 2,961,367 Patented Nov. 22, 19 60 lCQ aqueous solution, may be added before, after or along with the aqueous ketene dimer emulsion. As in the case of the preferred procedure, optimum results are obtained if the pH of the aqueous pulp suspension is maintained within the indicated range.

Some sizing of the paper by the ketene dimer will usually be developed during drying of the paper web' in accordance with conventional drying procedures utilized in the art. If desired, the sheet may be cured by heating to a relatively elevated temperature, say about 100 C., for a short period of time such as about 10 minutes. However, this is not necessary as adequate sizing develops on mere standing or storage at room temperature for a day or two.

Having described the invention generally, the following examples are given in illustration but not in limitation of the invention. All parts and percentages are by weight unless otherwise specified.

EXAMPLE 1 A portion of the alkylketene dimer emulsion was mixed with an aqueous 0.1% soluution of Polymin P,

a poly(ethyleneimine) manufactured by Badische Anilin' and Soda Fabrik, Ludwigshafen, Germany, having the following properties:

(1) Aqueous solution containing about solids (2) Molecular weight 30,000-40,000 (3) Nitrogen content about 16% The resulting mixture was then added to an unbleached kraft pulp, the proportions of ingredients being such as to provide 0.2% of the ketene dimer, based on the pulp and 0.005 of the poly(ethyleneimine) based on the pulp.

The unbleached kraft pulp had been beaten to 750 SR freeness and then dilutedin the proportioner of a Noble and Wood handsheet machine to a concentration of 0.25%. 1 Theketene dimer. emulsion and the poly(ethyl-; eneimine) 'solutio'nwere mixedfive minutes before being added to the pulp. I

One thousand parts of the thus-treated pulp were diluted to 10,000 parts in the deckle box of the handsheet machine and then formed into 8 x 8 handsheets. A series of 12 sheets was made in this manner and with the exception of the first sheet, each successive sheet was diluted with white water drained away from the preceding sheet.

The sheets were dried on a steam roll and then cured at C. for about 15 minutes. Sheets 1, 2, 3, 4, 7

and 12 were tested for sizing by noting the resistance in seconds to Superchrome Ink. The results are set forth in Table below:

Table 1 Percent Ink-Sheet No.

Example N 0. P013 (ethylene- The sizing, results obtained in Example 1 are superior to those. which are obtained with sheets similarly pre Resistance in Seconds to Superchrorne imine) 1 2 3 4 7 12 pared and tested but without the addition of Polymin P" thus indicating a greater degree of retention of the ketene dimer by the cellulose fibers.

EXAMPLE 2 A sample of bleached k'raft' pulp was treated, formed into sheets, and tes'tedas in Example 1 except that the proportions of ketene dimer and poly(ethyleneimine) were varied to provide 0.3% of the 'ketene dimer, based on pulp, and 0.05% ofthe poly(ethyleneimine) based on the pulp. The poly(ethyleneimine) used in these examples was Aquacel HW, a poly(ethyleneimine) put out by the American Aniline and Extract Company, Philadelphia, Pa. 'The resultsare set forth in Table 2 and 2, there is a greater improvement in sizing and thus in retention at the higher concentration of 0.05% poly- (ethyleneimine) than at the lower concentration of 0.005%. Thus while there is an appreciable improvement at the lower concentration, optimum results are obtained when the concentration of poly(ethyleneimine) is about 0.05% or more by weight based on the weight of dry pulp.

The ketene dimers which are particularly useful in the process of the present invention are dimers having the formula [RCH=C==O] where R is a hydrocarbon radical, such as alkyl having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl and alkaryl. In naming ketene dimers, the radical R is named followed by ketene dimer. Thus, phenyl ketene dimer is:

benzyl ketene dimer is:

and decyl ketene dimer is: [C H CH=C=O] Representative ketene dimers whose emulsions may be used in the process of the instant invention include octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, docosyl, tetracosyl, phenyl, benzyl, fi-naphthyl and cyclohexyl ketene dimers, as well as the ketene dimers prepared from montanic acid, naphthenic acid, A decylenic acid, d 'dodecylenic acid, palmitoleic acid, oleic acid, ricinoleic acid, petroselinic acid, vaccenic acid, linoleic acid, linolenic acid, eleostearic acid, licanic acid, parinaric acid, tariric acid, gadoleic acid, arachidonic acid, cetoleic acid, erucic acid and selacholeic acid, as well as ketene dimers prepared from naturally occurring mixtures of fatty acids, such as those mixtures found in coconut oil, babassuoil, palm kernel oil, palm oil, olive oil, peanut oil, rape oil, beef tallow, lard (leaf) and whale blubber. Mixtures of any of the above-named fatty acids with each other may also be used.

Aqueous emulsions of alkylketene dimers suitable for use in the process of the present invention are fully described in Us. Patent No. 2,627,477 to William Downey. However, particularly preferred are those emulsions which are prepared using a nonionic emulsifier. In addition to the nonionic emulsifiers specifically disclosed by Downey, those nonionic emulsifiers which have found to. be particularly useful include polyoxyethylene sorbi tan trioleate, sold by the Atlas Powder Company under the name Tween polyoxyethylene sorbitol hexaoleate, sold by the Atlas Powder Company under the trade name Atlox 1086; polyoxyethylene sorbitol laurate, sold by the Atlas Powder Company under the trade name Atlox 1045; and polyoxyethylene sorbitol oleate-laurate, sold by the Altas Powder Company under the trade name Atlox 1045A.

The aqueous emulsions and/or suspensions are-added to the paper pulp in amounts such as to produce a concentration of the ketene dimer in the aqueous pulp suspension of from about 0.01% to about 1% by weight based on the weight of dry pulp. The preferred concentration of ketene dimer is from about 0.1% to about 0.5% by weight based on the weight of dry pulp.

The poly(alkyleneimines) contemplated for use in the process of the present invention are water-soluble or water-dispersible substances formed by polymerizing an alkyleneimine containing not more than four carbon atoms. They may be prepared by carefully heating monomeric ethyleneimine, propyleneimine or butyleneimine in the presence of a catalyst as described, for example, in US. Patent No. 2,182,306 in connection with the preparation of poly(ethyleneimine). Such materials are commercially available in the form of conceittrated aqueous solutions such as Polymin P and Aquacel HW utilized in the examples. The higher molecular weight materials of this type generally give better results and are preferred.

In utilizing the poly(alkyleneimine) in the process of the present invention, an aqueous solution of same is added to the aqueous ketene dimer emulsion or to the aqueous suspension of paper pulp, depending on the particular procedure being used. The amount of poly- (alkyleneimine) utilized will vary, depending on a mum ber of factors but, in general, will be from about 0.001% to about 0.2%, and preferably from about 0.05% to about 0.1%, based on the pulp.

It will thus be seen that the present invention provides an improved process for the internal sizing of paper with aqueous emulsions of ketene dimers. While a preferred embodiment of the invention has been disclosed, the invention is not to be construed as limited by the specific details described except as they may be included in the following claims.

What I claim and desire to protect by Letters Patent 1. The process of sizing paper which comprises forniing an aqueous suspension of paper pulp, admixing with the aqueous suspension of paper pulp an aqueous ke tene dimer emulsion and a poly(alkyleneimine), the aqueous ketene dimer emulsion being added in an amount such that the concentration of ketene dimer in the aqueous suspension of paper pulp is from about 0.01% to about 1% based on the dry weight of pulp, the poly-' (ethylenirnine) being added in an amount such that the concentration thereof in the aqueous suspension of paper pulp is from about'0.00l% to about 0.2% based on the dry weight of pulp, and then forming the thus-treated paper pulp into sheets.

2. The process of sizing paper'which comprise's'forining an aqueous suspension of paper pulp, admixing with the aqueous suspension of paper pulp an aqueous ketene dimer emulsion and a polymer of an alky'leneimine containing not more than four carbon atoms, the aqueous ketene dimer emulsion being added in an amount such that the concentration of ketene dimer in the aqueous suspension of p'aper'pulp is from about 0.01% to about 1% based on the dry weight of pulp, the olymer of an alkyleneimine containing not more than 4 carbon atoms being added in an amount such that the concentration thereof in the aqueous suspension ofpaper pulp is from about 0.001% to about 0.2% based on the dry Weight Of P p, then forming the thus-treated paper pulp' into sheets, i

3. The process of claim 1 wherein the poly(alkyleneimine) is poly(ethyleneimine).

4. The process of claim 3 wherein the ketene dimer has the formula [RCH=C=O] where R is a hydrocarbon radical selected from the group consisting of alkyl groups having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl and alkaryl groups.

5. The process of sizing paper which comprises forming an aqueous suspension of paper pulp, admixing with the aqueous suspension of paper pulp a suflicient amount of an aqueous alkylketene dimer emulsion to supply from about 0.01% to about 1% alkylketene dimer based on the weight of dry pulp, said aqueous alkylketene dimer emulsion containing from about 0.001% to about 0.2% of poly(ethyleneimine) based on the weight of dry pulp, and then forming the thus-treated paper pulp into sheets.

6. Paper sized with from about 0.01% to about 1% of ketene dimer and from about 0.001% to about 0.2% of a polymer of an alkyleneimine containing not more than four carbon atoms, said ketene dimer having the formula [RCH=C=O] where R is a hydrocarbon radi- References Cited in the file of this patent UNITED STATES PATENTS 2,182,306 Ulrich et al. Dec. 5, 1939 2,765,228 Jordan Oct. 2, 1956 2,785,067 Osberg Mar. 12, 1957 OTHER REFERENCES Casey, I. P.: Pulp and Paper, vol. I, p. 599, Interscience Publishers, Inc., New York, 1952. Copy in Div. 25. 

6. PAPER SIZED WITH FROM ABOUT 0.01% TO ABOUT 1% OF KETENE DIMER AND FROM ABOUT 0.001% TO ABOUT 0.2% OF A POLYMER OF AN ALKYLENEIMINE CONTAINING NOT MORE THAN FOUR CARBON ATOMS, SAID KETENE DIMER HAVING THE FORMULA (RCH=C=012 WHERE R IS A HYDROCARBON RADICAL SELECTED FROM THE GROUP CONSISTING OF ALKYL GROUPS HAVING AT LEAST 8 CARBON ATOMS, CYCLOALKY GROUPS HAVING AT LEAST 6 CARBON ATOMS, ARYL, ARALKYL AND ALKARYL GROUPS 